


Begin Sync

by SoloShikigami



Series: Heat Sync [1]
Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell, Alternate Universe - Underswap, Angry Sex, CEO, Ecto-Genitalia, M/M, Mating Cycles/In Heat, Office Sex, Sans Swearing, Skele-Heat, Underfell Papyrus, Underswap Papyrus, Underswap Sans
Language: English
Status: Completed
Published: 2016-06-11
Updated: 2016-06-11
Packaged: 2018-07-14 08:27:09
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,458
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7162286
Author URL: https://archiveofourown.org/users/SoloShikigami/pseuds/SoloShikigami
Summary: <blockquote class="userstuff">
              <p>An interesting thing happens sometimes when certain monsters are in close proximity with one another; their heat syncs up.<br/>So what happens when they have to work on a project and no one is allowed to take a day off?<br/>Sans can usually work with anyone. Papyrus can usually never get along with anyone. Sans' patience will be tested and Papyrus is compelled to push the limits.</p>
            </blockquote>





	Begin Sync

**Author's Note:**

  * For [BattrelaRage](https://archiveofourown.org/users/BattrelaRage/gifts).



> Welcome to part one of my CEO series! Many thanks to [Eli](http://eli-sin-g.tumblr.com/) for igniting this fire.

            Sans knew this Papyrus was trouble the moment he walked into the meeting room. Being able to read people right off the bat was very valuable in this field but sometimes Sans wished he wasn't so good at it.

            Sans' corporation was teaming up with two others for a major project; one of the other companies he had teamed up with before and it was always a pleasure to work with them - he and their CEO had a lot in common, so much that sometimes Sans' assistant would comment that in some other dimension they would be twins.

            As for the other company, he had only spoken with some of their representatives via phone and email, but this was the first time he was meeting their CEO.

            Sans wondered if Papyrus was trying a little too hard in the intimidation department with his pressed, black slacks, a black dress shirt, and a satin, dark red tie. Sans could tell right away that there was no bluffing in his demeanor and appearance; he was a shark, someone who got what he wanted and didn't really care how he went about it and how many people were left in his wake.

            There were many reasons Sans didn't want to work with him, which meant of course, they were going to work together.

*~*~*~*~*~*~*~*~*~*~*~*~*~*~*

            “THAT SON OF A BITCH!”

            The swearing was enough to get the typically lazy assistant on his feet; the sound of glass breaking right afterwards made him break into a run.

            “Boss?!” Papy threw open the office door. “Sans?! Are you all right?!”

            Sans was leaning his head against the window, his left hand curled into his body, but Papy could see the bleeding magic dripping from it.

            “Oh, hell, Sans, what happened?” Papy quickly grabbed a few tissues and went over, carefully taking the injured hand.

            “Papyrus? Oh hey, Papyrus, good,” Sans murmured, sounding as if he had just woken up.

            “What the fuck happened?”

            “Language.”

            “Hey, you just swore yourself.”

            “Huh?” Sans looked lost for a moment, but then fire suddenly blazed in his blue eyes. “Right. That creep from Edge Inc. is really starting to annoy me.”

            “What did he do?” Papy led Sans over to the couch and made him sit while he looked for the first aid kit.

            “It’s what he keeps doing!” Sans grumbled, gesturing with his injured hand. “Every time we don’t agree on something, instead of talking and compromising and working it out, he jumps ahead and does what he wants!”

            Papy caught the injured hand gently and started cleaning and patching it up properly.

            “Is he hurting the project?”

            Sans huffed, covering his face with his other hand. “Well, yes and no? He has good ideas and he’s aggressive enough to get done what needs to be done, but a few of his decisions have almost set us back and this last one definitely will.”

            Papy listened and nodded and finished wrapping Sans’ hand with gauze.

            “All better,” Papy said with an indulgent smile. But Sans wasn’t even looking at him and it made him frown.

            Sans’ whole posture was beginning to worry him; he was tense, still very angry which was a little unlike him, and Sans didn’t seem to be concerned over his injury at all.

            “Hey, Boss, can I ask you something? Considering how well I know you and all?” Papy asked.

            “Yeah,” Sans said, sounding tired and not moving his hand from his face.

            “When is your next heat supposed to start?”

            Sans looked up at him with a frown. “Not for another three weeks, I think.”

            “Are you sure?”

            Sans scowled at him. “Of course I’m sure!”

            “Well, you seem to be in pre-heat.”

            Sans got to him feet in an angry huff. “Why would you think that? I’m angry! Justifiably so!”

            “Yes, but you usually don’t swear, break glass with your bare hand, and you didn’t flinch once while I was cleaning you and patching you. There are three butterfly stitches in the middle of your palm. Not for nothing, but you tear up at a papercut.”

            “Hey! Those hurt!”

            Papy stood and grabbed the wrist of Sans’ injured hand and lifted it a little roughly. Sans just glowered at him.

            “Does this hurt?” Papy asked.

            “No.”

            “It should. Also, you only give me that look and get this angry when you’re about to go into heat,” Papy lowered his hand with a sigh; him getting upset wasn’t going to help anything. Besides it took too much energy. “I think you need to take some time off.”

            Sans’ anger faded as the words sank in and it all began to make sense. His hand began to ache as he came back to himself. He started breathing hard and he reached up to loosen his tie.

            “I can’t, they’re not letting anyone take any time off until this whole thing is finished and we still have weeks to go,” Sans murmured, beginning to pace. “Oh, stars, what am I going to do? I can’t let that jerk see me like this!” He stopped pacing, squeezing his hands into fists and he spun to look at Papy. “No! I can and _will_ do this! After all, they don’t call me the Magnificent Sans for nothing!”

            Papy smiled at him. “Got that right, also, I’ll be here for you.”

            Sans smiled warmly at him. “Thanks Papy.”

*~*~*~*~*~*~*~*~*~*~*~*~*~*~*

            “What do you mean they sent you to the other building for the next two weeks?!?” Sans tried to not scream into his cell phone.

            “It’s what President Gaster ordered,” Papy said, not sounding too happy either. “I mean, I can’t say no, right?”

            Sans sighed. “No, no you can’t; you may work for me but Gaster’s word supersedes all.”

            “Are you going to be all right?”

            “Of course I am!” Sans immediately switched gears. “Look, this is a great opportunity for you to learn more about networking and meeting some other people we may be dealing with in the future! I want you to do us proud; dress your best, work hard, and show them what we’re made of!”

            Papy snickered. “You got it, Boss.”

            “Mweh heh heh. I’ll see you in a couple of weeks, Papy!”

            Sans hung up and sunk onto his bed with a shudder.

            He was so, so screwed.

*~*~*~*~*~*~*~*~*~*~*~*~*~*~*

            “Absolutely not!” Sans slammed his hands down on the table as he got to his feet. “I’ve let just about every other thing you’ve done in the past month slide, but this is ludicrous! You’re going to destroy everything!”

            Papyrus snarled at him but stayed seated with his arms and legs crossed. “And you are too much of a pussy pansy to get shit done!”

            “You _know_ how I feel about swearing; not in my office!”

            “And it’s worrying over stupid shit like that that’s keeping you and your company stuck!” Papyrus got to his feet and also slammed his hands on the table, glowering at the shorter skeleton across from him. “I’m sure you’ve seen the numbers; my company is light years ahead of yours.”

            “At what cost, I wonder? I see how you talk to people and how you treat your employees; your own assistant is scared of you!”

            Papyrus stood up straight, taking a deep breath in through his nose, and stalked around to the other side of the table to tower over Sans. He was a little surprised that instead of shrinking back like he figured the smaller skeleton would, he instead met his glare with one of his own and was standing his ground.

            “You leave my assistant out of this,” Papyrus growled in a low and dangerous tone.

            Sans felt an odd shudder starting at his tailbone.

            ‘ _What? No, no, no, body, don’t do this to me now,_ ’ Sans thought in the back of his mind in a panic.

            Now that Papyrus was this close, he caught an odd smell coming off of Sans. He furrowed his brow a little as he breathed in deeply but quietly; as the scent entered him he felt his body flush.

            ‘ _What the fuck?_ ’ Papyrus thought to himself.

            Sans started noticing a certain smell coming from Papyrus and it was sending parts of his body into overdrive.

            ‘ _What in the world?_ ’ Sans wondered.

            ‘ _Is he-?_ ’

            ‘ _He can’t possibly be-?_ ’

            Neither could help the look of realization, melting the anger off of their faces.

            ‘ _We fucking synced,_ ’ they both thought.

            Sans yelped as he was suddenly picked up and slammed on the table and before he could protest, sharp teeth pressed against his own. Not willing to submit completely, Sans reached up and started tearing at Papyrus’ black shirt.

            “I really fucking hate you, you know that, right?” Papyrus growled, leaning down to bite Sans on the neck.

            “Urk!” Sans gasped at the bite, but then growled as he reached up to push Papyrus’ head back so he could bite his neck too.

            Sans wasn’t going to lie; hearing a moan coming from Papyrus was a turn on.

            “I don’t like you all that much either,” Sans grumbled, licking the long neck and across his clavicles as sharp fingers did away with his tie and started returning the favor of torn clothing.

            “You’re such a fucking pussy,” Papyrus growled, pushing the shirt apart and leaning down to lick and bite at Sans’ ribcage. “I’m willing to bet that’s what you form when you go into heat.”

            “Oh yeah? You may be a dick but I doubt you know how to use yours,” Sans snapped in return, squirming under the attention.

            Papyrus snarled and got back up, gripping Sans firmly around his neck. “I’m going to fuck you so hard you won’t be able to walk straight for a week.”

            “I’ll make you cum so hard you’ll pass out for days,” Sans growled back, clawing at the hand around his neck. “I bet you wouldn’t last a minute with me.”

            In a surprising show of strength and skill, Papyrus found himself rolled over and Sans on top of him and one of his hands pinned. Sans’ other hand worked at his belt while his broad blue tongue licked along his bottom ribs. Papyrus groaned, arching into the wet touches. The only reason he was letting this little shit of a blueberry continue was to prove that yes, the Great Papyrus could most definitely last more than a minute.

            Sans decided to make it his personal mission to draw out as many groans and twitches from the taller skeleton; pulling such sounds from a monster with such a strong personality was touching something deep inside of him.

            Papyrus grunted as Sans yanked his pants off, and he was sure the little skeleton didn’t even look at the rod of red magic before taking as much of it into his mouth as he could. He smirked, realizing he was correct, as Sans bobbed his head a couple of times, his tongue running along the underside, but then he slowed and dragged his tongue a little more carefully, which made Papyrus groan but he chuckled darkly at the same time.

            “Found the piercings, didn’t you?” Papyrus all but purred, sitting up without disturbing Sans’ motions.

            Sans went to pull off, but a hand on the back of his head kept him where he was. He looked up at the other skeleton’s face and was annoyed at the smirk he was being given.

            “Yeah that was a surprise for my Sans as well,” Papyrus murmured, shifting his hips up into the warm mouth. “Can you just imagine those two little points of metal rubbing your insides? Feel them against your tongue? Yeah, imagine that inside your cunt.”

            Sans couldn’t help moaning and then choked as Papyrus took the opportunity to buck further into his mouth. Sans grunted and glared, then closed his eyes and concentrated on showing this rude skeleton what he was capable of.

            One thing Sans could do with his tongue was curve it into a “U” shape; he took Papyrus in as deep as he could, curved his tongue around him, then scrapped the top of the cock with his teeth as he dragged back slowly. Papyrus groaned and tried to move deeper into Sans’ mouth, but Sans finally got his hands settled on the taller skeleton’s pelvis to keep him from thrusting up. Sans felt the sharp fingertips gripping the back of his skull, but a quick swipe and a hum around the rod released his head from Papyrus’ grasp.

            Papyrus gave in for the moment, leaning back on his elbows and watching his cock moving in and out of a mouth that he was loathe to admit was very talented. His eyes rolled back a little when Sans started to hum around him. Sans glanced up and was pleased at the look on Papyrus’ face. He dragged one hand lower, pressing just below the base of Papyrus’ dick, searching.

            Papyrus’ eyes flew open.

            “Oh fuck no,” Papyrus growled, reaching down and gripping Sans by the back of his shirt and jacket.

            Sans had no idea anyone could move as fast as Papyrus. He felt like the wind was knocked out of him as his back met the table.

            “Nice try, squirt,” Papyrus murmured, leaning into his neck to bite it. “You should have just stuck to what you do best, you dirty cocksucker.”

            “Oh shove it, you liked it,” Sans murmured, arching up into the other skeleton.

            Papyrus chuckled.”Ohh, not as much as you're going to like this.”

            Sans whimpered as Papyrus squeezed his neck lightly before moving to shove Sans' pants off. As he predicted, a soft, glowing blue mound dripping with desire and magic met his eyes. He leaned in and dragged his tongue across the whole slit, making Sans cry out. Papyrus reached up and slammed a hand over Sans' mouth.

            “You don't really want to have someone come in to find us like this, do you?” Papyrus purred.

            “I'll tell them to flip off and mind their own darn business,” Sans growled around his long fingers.

            Papyrus rolled his eyes and flicked his tongue into the folds lightly, drawing a quieter gasp from Sans.

            “You know, you always did seem a tad uptight,” Papyrus murmured, his tongue reaching in for a lick between words while his fingers played just outside the dripping hole. “Maybe if you swore now and then, you wouldn't be so tense.”

            “Why? Does it make you angry?” Sans said with a smirk, wriggling under Papyrus' touches.

            “Unbelievably so,” Papyrus growled.

            Papyrus suddenly shoved Sans' legs further apart and drove his tongue as deep in his hole as he could. Sans had been trying to keep quiet, but the muffled cry and wriggling only spurred Papyrus' efforts on.

            It didn't last long; Papyrus sated his curiosity on how the smaller skeleton tasted and moved up to kiss him deeply to share it. Sans seemed a little unwilling, turning his head in an odd aborted version of avoidance, but he moaned upon feeling the taste of his own magic on his tongue.

            “You're dying to have me fuck you, aren't you?” Papyrus growled.

            Sans glared daggers at him and looked away.

            “Nah, you don't suck my dick and let me eat you out and then act all high and mighty because you don't swear.”

            Papyrus moved himself so the head of his cock rubbed against Sans' soft folds, making the smaller skeleton squirm in an attempt to line Papyrus up with his hole.

            “Ask me nicely,” he murmured against Sans' skull.

            Sans whimpered and shook his head, wriggling more. Papyrus reached down with on hand and pressed it low on Sans' spine, keeping him from wriggling too much and drawing a desperate moan from his mouth.

            “Ask me,” Papyrus growled, licking up his neck.

            “N-n-no,” Sans stammered, still attempting to keep some semblance of control.

            “Come on, you know you want it badly. So badly. I can feel how hot you are, your scent is overwhelming, and if you don't, I might just take you anyway. When you're in heat, you really don't care who it is.”

            Sans whined and arched his back, or tried to, but couldn't get far.

            “Please, Papyrus,” he whispered.

            “Hm?” Papyrus leaned down to lick his neck again.

            “Please, just... please take...”

            “Come on, ask.”

            “Take me, dammit! Just fucking take me!”

            Sans' hands flew to his mouth as his face turned a medium blue with a blush.

            “Look at that, you can swear,” Papyrus said, taking a little pity on the smaller skeleton and pressing himself inside of him carefully.

            Sans covered his eyes with one hand and bit down on his other arm with a whine that heightened in pitch the deeper Papyrus pressed inside.

            “Don't give me that,” Papyrus chastised with a small chuckle, drawing out as slowly as he went in. “Admit it, you liked it.”

            Sans whimpered. “I did, and I hate it.”

            Papyrus chuckled and moved back inside of him.

            Sans wriggled underneath the bigger skeleton. Papyrus wasn't exaggerating when it came to his piercings; Sans could feel the metal nubs rubbing inside of him and it added a whole new dimension to the experience, stimulating him more and quickly drawing desperate gasps and moans out of him. Papyrus had gathered his wrists in one hand and pinned them above him head as he drove faster and harder.

            “Fuck, this feels so fucking good,” Papyrus growled.

            “Yes, yes, oh stars, yes,” Sans groaned.

            “Nyeh heh heh heh heh, so you admit you liked getting fucked by me? You like being driven into over and over, having my long, hard cock inside of you,” Papyrus picked up the pace. “Come on; tell me how much you like getting fucked like this.”

            “It's good, so good,” Sans whimpered.

            “No, I want to hear you _say it_.”

            Through the fog of his heat-driven desire the words made more sense and he felt himself blush again.

            “Don't make me.”

            “Come on, say it.”

            “You are such a jerk!”

            “Say it.”

            Papyrus began to slow down, though it took every ounce of his self-control to not just pound Sans into the table.

            “Say it,” he hissed when Sans made no response.

            Sans made a small squeaking sound.

            “What was that?”

            “... ff... me...”

            Papyrus pulled out very slowly until the head was just barely inside Sans' hole.

            “Say. It. Now.”

            Sans' whole body jerked.

            “DAMN IT PAPYRUS FINISH FUCKING ME OR ELSE!”

            Papyrus was taken aback for a split second, because not only did the usually polite skeleton swear loudly (and so lewdly), but an animalistic tone and look appeared on his face that Papyrus couldn’t deny, and so he gave Sans what he wanted.

            Sans cried out as Papyrus drove into him hard and fast; it hurt but it also felt so good that he never wanted him to stop.

            Papyrus grunted as he let his own instincts take over, slamming over and over again into the willing body beneath him. Sans' heat scent was making him dizzy, it mixed with his own and created an odd perfume that made him feel numb on the outside but he burned from within. He knew that it was doing the same to Sans.

            “Papyrus,” Sans moaned. “I’m so close, so close.”

            “Just a little longer,” Papyrus groaned in return.

            Sans’ moans grew louder, which only pushed Papyrus further towards the edge, until he reached down with one hand to rub Sans clit.

            “Gaaaahhh!!” Sans screamed as his orgasm hit, his body arching and nearly throwing Papyrus off of him.

            Papyrus growled, sounding like a feral animal as he thrust a few more times before he unloaded into Sans’ twitching body. Red and pale blue magic coated them both, and Papyrus only had enough in him to collapse next to Sans so he didn’t crush him. The two skeletons lay on the table, breathing hard, both barely conscious as their bodies cooled and their magic dissipated.

            “I still think you’re a pussy,” Papyrus murmured after nearly ten minutes of silence.

            “I still think you’re a jerk,” Sans said with a slight sniff, his hands slowly moving to his shirt to assess how many buttons he had left.

            “I didn’t pass out.”

            “I can still walk.”

            “Are you implying something?”

            “Are you?”

            “You know what? Fuck you.”

            Sans smirked. “Already did, you dingus.”

            Papyrus growled, gripping Sans by the lapels and pulling him so they were face to face.

            “You make it really easy to despise you,” Papyrus grumbled.

            “The feeling is mutual,” Sans said, tilting his head up slightly.

            Papyrus’ eye twitched, and then he yanked Sans forward for a kiss.

            Sans decided that was one decision of Papyrus’ he would just go along with.

**Author's Note:**

> Come visit me on [Tumblr,](https://soloshikigami.tumblr.com/) feel free to make any requests/suggestions for the series, and thank you for reading!


End file.
